1. Field of the Invention
The present disclosure relates to proximity, color, gesture, and/or motion sensors, particularly optical sensors having a molded or cast infrared light blocking compound.
2. Background
Proximity, color, gesture, and motion sensors are often used in a variety of devices, including mobile phones, personal media players, tablet computers, laptop computers, amusement and vending machines, industrial machinery, contactless switches, automated sanitary machinery, and other devices. By way of a non-limiting example, some mobile phones incorporate a proximity sensor near the mobile phone's touchscreen so that the screen can be turned off to save power and to avoid unwanted touch inputs when the mobile phone is being used and a user's head is near to the screen or is touching the screen.
FIG. 1 depicts a prior art optical proximity sensor 100. Optical proximity sensors 100 can comprise one or more light emitters 102 and one or more light detectors 104. In some embodiments, the light emitters 102 can be light emitting diodes (LEDs) that emit infrared light, and the light detectors 104 can be photodiodes configured to detect infrared light. As can be seen from FIG. 1, when an object 108 is located proximate to the optical proximity sensor 100, infrared light 106 emitted by the light emitter 102 can be reflected off of the object 108 and be directed back toward the light detector 104. The reflected rays of infrared light 106 can be detected by the light detector 104, which can provide an indication that the object 108 is proximate to the optical proximity sensor 100, and/or can provide information about the motion of the object 108 relative to the optical proximity sensor 100 such that the optical proximity sensor 100 can act as a motion sensor or gesture sensor.
Crosstalk can be undesirable interactions between the light emitters 102 and light detectors 104 in optical proximity sensors 100. Crosstalk can occur when light travels directly or indirectly from the light emitter 102 to the light detector 104 without being reflected off of a nearby object 108, thereby leading to false positives in motion or proximity detection. To decrease the level of crosstalk between the light emitters 102 and light detectors 104, many optical proximity sensors 100 have one or more blocking components 110 placed or formed between the light emitters 102 and light detectors 104 to block at least some non-reflected light transmission between the light emitters 102 and the light detectors 104.
In many optical proximity sensors 100, the blocking component 110 can be a shield, such as a metal shield or a shield of any other material that blocks the transmission of infrared light. Shields are often manufactured separately, and are placed between the light emitter 102 and light detector 104 during assembly of the optical proximity sensor 100, as shown in FIG. 1. However, the use of a separately manufactured metal shield can add manufacturing expenses due to the materials cost of the metal or other infrared-blocking material, the often small size of the shields, and the cost of custom machinery to form the shield and to place the shield during assembly. Additionally, the shield can be dented or deformed during use, or can come loose and be displaced from the rest of the optical proximity sensor 100. As the placement and structural form of the blocking component 110 can be important in inhibiting light transfer in certain directions to limit crosstalk, deformation or displacement of the shield can lead to decreased performance of the optical proximity sensor 100 by allowing higher levels of crosstalk.
In other optical proximity sensors 100, the blocking component 110 can be a light blocking compound 112 that blocks transmission of substantially all light within a particular spectrum through the light blocking compound 112, as shown in FIG. 2. Optical proximity sensors 100 that comprise light blocking compounds 112 have traditionally been formed using a double mold process in combination with light transmissive compounds 114 that allow the transmission of substantially all light within a particular spectrum.
In a double mold manufacturing process, light transmissive compounds 114 are first encapsulated over a light emitter 102 and light detector 104. The light transmissive compounds 114 are molded over and around the light emitter 102 and light detector 104, and are allowed to cure. After the light transmissive compounds 114 have cured, the light blocking compound 112 is molded over and around the light transmissive compounds, filling a space between the light emitter 102 and light detector 104 as shown in FIG. 2, such that light emitted by the light emitter 102 will be blocked by the light blocking compound 112 from passing directly to the light detector 104. The light blocking compound 112 is generally molded to leave apertures 116 above the light emitter 102 and light detector 104, such that light emitted by the light emitter 102 can pass through the light transmissive component 114a encapsulating the light emitter 102, exit the proximity sensor 100 through the aperture 116a above the light emitter 102, be reflected by an external object 108, re-enter the proximity sensor 100 through the aperture 116b above the light detector 104, pass through the light transmissive component encapsulating the light detector 104, and finally enter the light detector 104 itself to be detected.
However, this double mold process can be expensive due to the need to use two different types of molding compounds. It can also take a long time, because the light transmissive compounds 114 must first be molded and allowed to cure over the light emitter 102 and light detector 104, and only then can the light blocking compounds 112 be molded over the previously molded light transmissive compounds 114. Additionally, special molds must be made and used to form apertures 116 that keep the light blocking compound 112 from completely covering the light transmissive compounds 114.
What is needed is an a sensor with a layer of light blocking compound directly covering and encapsulating a light emitter and light detector, such that the light blocking compound blocks crosstalk between the light emitter and light detector, but does not fully block transmission of light out of and into the sensor.